Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of etching an organic anti-reflective coating, which is suitable to minimize the loss of a photoresist film and to improve an anisotropic etch profile.
In general, the use of a bottom organic layer as an anti-reflective coating for i-line and deep microlithography (DUV) is rapidly increasing, recently.
An organic anti-reflective coating (ARC) has an aromatic polysulfone structure which has the following functional units: ##STR1##
In other words, in case that a component constituting the anti-reflective coating has the above aromatic polysulfone structure), it is used as an available anti-reflective coating for the DUV microlithography.
The organic layer has a carbon (C) of the aromatic radical as a main component, and has another components such as S.dbd.O,H. Thus, in order to etch such organic layer, there is utilized an O.sub.2 plasma in etching of a down stream type or a plasma type, or in a reactive ion etching (RIE) equipment.
However, due to the chemical reaction characteristics between the bottom organic anti-reflective coating and the O.sub.2 plasma, an anisotropic etch profile occurs when etching the organic anti-reflective coating, whereby a serious critical dimension (CD) bias is caused.
Discussion of Related Art
In order to solve the aforementioned problem, a polymer was formed on the sidewall of an organic layer for used as the anti-reflective coating, in the past.
Hereinafter, the conventional method of etching an organic anti-reflective coating will be described with reference to the attached drawings.
FIGS. 1a to 1c are cross-sectional views for illustrating the conventional method of etching an organic anti-reflective coating.
To begin with, as shown in FIG. 1a, an organic anti-reflective coating 2 is formed on an etch layer 1, i.e. a layer to be etched.
A photoresist material 3 is coated on the organic anti-reflective coating 2, and then, patterned through exposure and development processes.
As shown in FIG. 1b, by adding a gas such as N.sub.2, CHF.sub.3, CF.sub.4 or C.sub.2 F.sub.6, that is, a compound gas containing N.sub.2 or F, to an O.sub.2 plasma, etching of the down stream type can be carried out. Also, the etching process may be performed in equipment such as the reactive ion etching type (RIE) or the magnetically enhanced reaction ion etching type (MERIE).
At this time, due to the added gas, a polymer 4, such as for example, CNx, CHFx or CFx, is formed at both sides of the organic anti-reflective coating 2 under the photoresist 3.
Further, on the surface of the etch layer 1, on which the organic anti-reflective coating 2 is removed, a residue 5 consisting of CF or CN collects.
Then, as shown in FIG. 1c, the photoresist 3 is removed. Using the organic anti-reflective coating 2 as a mask, the etch layer 1 is selectively removed, thereby completing the processes in accordance with the conventional method.
However, the conventional method of etching an organic anti-reflective coating has the following problems.
First, since a heavy gas such as CHF.sub.3, CF.sub.4 or C.sub.2 F.sub.6 is added, the photoresist is damaged due to an increase in the ion sputtering effect within the plasma.
Secondly, due to the damage of the photoresist, the etch selectivity between the photoresist and the organic anti-reflective coating is less than 1:1. Thus, accurate etching cannot be accomplished in the etch layer.
Thirdly, in addition to the sidewall of the organic anti-reflective coating, the polymer such as CHFx or CFx is formed on the etch layer located thereunder, thereby preventing an accurate etching of the etch layer.